It is often not clear whether individuals claiming to be a “patent adviser” or “patent expert” are competent or not. They are not certified by the authorities and have not passed any examinations showing that they have sufficient knowledge of patent law to be able to advise you properly.
All Dutch patent attorneys are a member of this Institute which maintains a register of patent attorneys. If a person is not in this register, you can assume that the person is not a Dutch patent attorney. If on the other hand a person is registered, you can then assume that this person is expert and professional.